Portail HAL IMT Mines Albi
Not a member yet
5440 research outputs found
Sort by
Absorption of Acid Gases: Evaluation of Thermodynamic and Kinetic Aspects of an Aqueous Solution of 2-(2-Diethylaminoethoxy) Ethanol and 1,3-Dimethyl-2-imidazolidinone
No full textInternational audienceThe removal of CO2 and H2S from a gas by absorption with an aqueous alkanolamine solution is an energy-intensive process. The addition of a physical cosolvent might lower the regeneration energy but also affects the thermodynamics and kinetics of acid gas absorption. In this work, we study the impact on the thermodynamics and kinetics of CO2 and H2S absorption of the addition of 1,3-dimethyl-2-imidazolidinone (DMI) to the aqueous 2-(2-diethylaminoethoxy)ethanol (DEAE-EO) solvent. A comparison is made with the impact of DMI on an aqueous methyldiethanolamine (MDEA) solvent. In all cases, DMI reduced the solubility and the absorption rate of the acid gases. DMI also reduced the initial kinetic H2S/CO2 selectivity, although this effect seems much more pronounced in aqueous MDEA than in aqueous DEAE-EO. The equilibrium thermodynamic H2S/CO2 selectivity is higher in the presence of DMI
Effect of ethanol on supercritical CO<sub>2</sub> solvent densities
No full textInternational audienceThe development of new industrial applications in the pharmaceutical, food, and cosmetic f ields uses supercritical carbon dioxide as a solvent or antisolvent in their processes for extracting non-polar molecules. Ethanol (EtOH) is added in small quantities to isolate a polar molecule during a unit operation by solubilization or precipitation. Density measurements in pure carbon dioxide (CO2) and in binary CO2-EtOH mixtures with mass compositions (ωCO2 = 0.99 and (ωCO2 = 0.98) were carried out using a vibrating tube densimeter. The isotherms were determined at temperatures of 303, 308, and 313 K, above the critical temperature, and for a pressure range from 5 to 10 MPa. Fine modeling around the critical point was performed using cubic equations of state with two or three parameters (Peng-Robinson and Coquelet-El Abbadi-Houriez EoS). The Huron-Vidal mixing rule coupled with the NRTL model was employed. To enhance the prediction around the critical point of pure carbon dioxide and binary CO2-EtOH mixtures, White’s correction method was used. The results for pure supercritical carbon dioxide show modeling performance with a deviation of 5.8% around the critical point
Vapor–Liquid Equilibrium Data and Thermodynamic Modeling for Binary Systems Consisting of Perfluorobutane (R610) with Oxygen or Nitrogen at (293, 313, and 333) K
No full textInternational audienceIsothermal vapor–liquid equilibrium (VLE) data for the oxygen or nitrogen with perfluorobutane (R610) systems are presented. The measurements were performed at three temperatures (293, 313, and 333) K and pressures up to 17.014 MPa using a static-analytic apparatus fitted with a rapid online sampler injector, a reliable tool for sampling equilibrium phases. The measurement uncertainties were within 0.04 K for temperature, 0.008 MPa for pressure, and 0.04 for mole fractions. The experimental VLE data for both systems were successfully modeled using the direct method and adjusted through the flash calculation objective function. The modeling approach combined the Peng–Robinson equation of state with the Mathias–Copeman alpha function and the Wong-Sandler mixing rule utilizing the nonrandom two-liquid activity coefficient model
Microfluidic reactor development for isothermal kinetic measurements of sugars hydrolysis and global kinetics determination by model-fitting approach.
No full textInternational audienceIn this study, a novel method was developed to understand the liquid-state reactions occurring inside the intermediate liquid component (ILC) during biomass fast pyrolysis. A new experimental setup using a heated 300 μm inner diameter capillary microchannel with flow visualization was designed to study isothermal kinetics and reaction mechanisms of liquid-state sugar hydrolysis reactions. Heat- and flow patterns were investigated to confirm the intrinsic character of the kinetic measurements. Following the conventional dimensional analysis, observations with a high-speed camera and computational fluid dynamics modelling (CFD) in COMSOL Multiphysics® were used to confirm the hydrodynamic slug-flow pattern and the scale function of the temperature. The microfluidic reactor can operate within a temperature range of 453-533 K, up to 7 MPa, and a residence time within the hot section of 5 to 80 s, which is controlled by the volumetric flow rate. The novelty of this reactor is that under the specified operating conditions and residence times, it can provide isothermal measurements of intrinsic reaction kinetics, which have never been reported for hydrolysis systems. After hydrolysis in the microfluidic reactor, liquid samples were analysed off-line through HPLC to determine the sugar conversion and product yields. A fitting kinetic approach was developed to treat the kinetic data and extract intrinsic kinetic parameters describing sugar hydrolysis, key reactions occurring in the softening phase of biomass fast pyrolysis that are too often overlooked. It is proposed to integrate this experimental kinetic information to complete biomass fast pyrolysis models to take into consideration the solvent-like reactional environment
Soot formation during oxy-steam-reforming of biomass pyrolysis volatile matters: validation of a chemical model
No full textInternational audienceThe conversion of solid biomass into fuel gas can be carried out by gasification. Biomass pyrolysis is the first step, and produces volatile matters (VMs) that consist of permanent gases and tars. Their noncatalytic conversion into syngas in a few seconds can be carried out at high temperatures, typically 1200 °C. This complex process involves three main types of reactions: (i) thermal cracking, (ii) the reaction with water vapor called steam reforming, and (iii) in certain cases reactions with oxygen for oxy-steam reforming. The VM conversion operation is known to have a major drawback: the formation of soot, sometimes in very large quantities. In this paper, pilot-scale experiments are carried out on the conversion of reconstituted VM under increasingly complex thermochemical conditions: cracking, steam reforming, and oxy-steam reforming. The soot yield is always superior to 0.5 g/g of tar. A numerical model is then proposed in order to describe the different situations. The model predicts accurately the quantities of soot formed in all situations, along with the composition of the gas phase. The effects of H2O and O2 addition on soot formation are identified using the validated model
Influence of Drying Techniques on the Properties of Cellulose Aerogels
No full textInternational audiencePaper and cardboard comprise about 20% of municipal solid waste [1]. Although recycling is a viable solution, its effectiveness is constrained by cellulose fiber degradation, which limits reuse to only three to five cycles before virgin fibers are required to maintain material quality [2]. This highlights the necessity for innovative methods to upcycle these materials into high-value products, such as bio-aerogels. Cellulose-based bio-aerogels possess remarkable properties, including high porosity (>90%), open-pore nanostructures, specific surface areas of 200–400 m²/g, and low density (0.05–0.2 g/cm³). These characteristics render them highly suitable for a broad spectrum of applications, including thermal insulation, catalysis, drug delivery, electrochemical processes, adsorption, separation, and the food industry [3]. Aerogel production involves drying a gel while preserving its porous structure, with the drying process defining the final properties [4]. Additionally, carbonization under a protective atmosphere can further enhance functionality, yielding carbon aerogels with expanded applications.This study explores the conversion of cellulose fibers obtained from paper and cardboard into bio-aerogels and carbon aerogels, with a focus on evaluating the influence of different drying techniques - supercritical CO₂, evaporative low vacuum drying, and freeze-drying - on material structural and functional properties. Microcrystalline cellulose was used as a reference and pulp fibers were dissolved in an 8% NaOH-water solution, with supercritical CO₂ drying incorporating a recycling loop to enhance sustainability. Subsequent carbonization was employed to produce carbon aerogels. The research systematically analyzed the effects of drying methods and carbonization on key properties such as shrinkage, porosity, density, and morphology. The findings aim to optimize production processes and enhance aerogel performance for diverse industrial applications.Acknowledgements: The authors are grateful to the Occitanie Region and ANR (PEPR "Recyclage, recyclabilité, ré-utilisation des matières" and “Investissements d’Avenir” program, ANR-18-EURE-0021 project) for funding.References:[1]“What a Waste 2.0: A Global Snapshot of Solid Waste Management to 2050,” Sep. 2018, doi: 10.1596/978-1-4648-1329-0.[2]N. J. Schenk, H. C. Moll, and J. Potting, “The Nonlinear Relationship between Paper Recycling and Primary Pulp Requirements: Modeling Paper Production and Recycling in Europe,” J. Ind. Ecol., vol. 8, no. 3, pp. 141–162, Jul. 2004, doi: 10.1162/1088198042442379.[3]T. Budtova, “Cellulose II aerogels: a review,” Cellulose, vol. 26, no. 1, pp. 81–121, Jan. 2019, doi: 10.1007/s10570-018-2189-1.[4]S. Zhao, W. J. Malfait, N. Guerrero‐Alburquerque, M. M. Koebel, and G. Nyström, “Biopolymer Aerogels and Foams: Chemistry, Properties, and Applications,” Angew. Chem. Int. Ed., vol. 57, no. 26, pp. 7580–7608, Jun. 2018, doi: 10.1002/anie.201709014
Optimisation de la gazéification des déchets de mangue et de la balle de riz pour une production d’énergie durable
No full textInternational audienceTo enhance the valorization of abundant resources such as mango waste and rice husk, this study investigates the feasibility of using different types of mango biomass and rice husk for efficient energy production through gasification. Aspen Plus simulation, validated by an experimental study, was adopted to explore the gasification potential of rice husk (RH) and mango waste specifically mango kernel (MK), mango seed (MS), and mango pericarp (MP) for thermochemical energy recovery. A sensitivity analysis of the gasification parameters, including reactor temperature, equivalence ratio (ER), and air-to-fuel ratio provided crucial insights into the performance of each biomass type. The results showed that MP achieved the highest cold gas efficiency (CGE) at 84.36%, followed closely by MK, MS, and RH. MP also had the highest carbon conversion efficiency (CCE) at 93.70%, while MK, MS, and RH had CCE of 88.33%, 85.76%, and 71.16%, respectively. RH required the lowest equivalence ratio (ER) and air/fuel ratio. MP, MK, and MS required ER values of 0.10, 0.16, and 0.17, respectively, with MS needing temperatures above 950°C for efficient char gasification. The turbine power output was similar across the biomasses, with MK leading at 351.17 kW. These promising results demonstrate the significant energy potential of these four resources, providing valuable solutions to facilitate the implementation of gasification processes by manufacturers and the validated Aspen Plus model can be used to scale up the gasification process, offering time and cost savings.Pour renforcer la valorisation de ressources abondantes telles que les déchets de mangue et la balle de riz, cette étude examine la faisabilité de l’utilisation de différents types de biomasse de mangue et de balle de riz pour une production d’énergie efficace par gazéification. Une simulation sous Aspen Plus, validée par une étude expérimentale, a été utilisée pour explorer le potentiel de gazéification de la balle de riz (RH) et des déchets de mangue, en particulier le noyau de mangue (MK), la graine de mangue (MS) et le péricarpe de mangue (MP), en vue d’une récupération thermochimique d’énergie. Une analyse de sensibilité des paramètres de gazéification, incluant la température du réacteur, le rapport d’équivalence (ER) et le rapport air/carburant, a fourni des informations essentielles sur les performances de chaque type de biomasse. Les résultats ont montré que le péricarpe de mangue (MP) atteignait la plus haute efficacité en gaz froid (CGE) avec 84,36 %, suivi de près par le noyau de mangue (MK), la graine de mangue (MS) et la balle de riz (RH). Le MP présentait également la plus forte efficacité de conversion du carbone (CCE) avec 93,70 %, tandis que MK, MS et RH affichaient respectivement des CCE de 88,33 %, 85,76 % et 71,16 %. La balle de riz (RH) nécessitait le plus faible rapport d’équivalence (ER) et le plus faible rapport air/carburant. Le MP, le MK et le MS nécessitaient respectivement des valeurs d’ER de 0,10, 0,16 et 0,17, le MS demandant des températures supérieures à 950 °C pour une gazéification efficace du charbon résiduel. La puissance produite par la turbine était similaire pour les différentes biomasses, avec un maximum observé pour le MK à 351,17 kW. Ces résultats prometteurs démontrent le potentiel énergétique considérable de ces quatre ressources et offrent des solutions pertinentes pour faciliter la mise en oeuvre des procédés de gazéification par les industriels. De plus, le modèle Aspen Plus validé peut être utilisé pour l’optimisation et le passage à l’échelle du procédé de gazéification, permettant ainsi de réaliser des économies de temps et de coûts
Experimental and DFT study of NOx decomposition via macroalgae-based biochar catalysts
No full textInternational audienceNitrogen oxides (NOx), mainly produced by high-temperature combustion processes, are responsible for severe environmental and health issues such as acid rain, ozone layer depletion, and respiratory diseases [1]. As a result, thermal NOx production may occur both for fossil and biosourced fuels, which points out an imperative need for exhaust gas post-treatment for NOx abatement (deNOx). In this sense, selective catalytic reduction is one of the most efficient technologies. This technology uses noble metal catalysts such as platinum and palladium, which present a high cost, toxicity and environmental impact [2]. The use of biosourced materials naturally rich in metals to replace commercial catalysts was shown as a promising alternative through the use of fern and willow catalysts rich on nickel and iron [3]. However, other resources naturally rich on iron, as a less toxic metal, should be explored [4]. In this context, this work aims to explore biosourced catalysts for deNOx by assessing the influence of the resource composition, operating conditions, catalyst deactivation and recycling. A modeling approach based on DFT calculations is used for a studying NO adsorption and catalytic conversion mechanisms through biochar surface chemistry
